For female registered users, ‘message’ feature is free. So they can send messages to any registered user without any restriction.
But for a male registered user, he should first upgrade himself to a premium user on the XOXO Tours app to be able to send or respond to messages to any registered user. Also a male premium user can only initiate a chat with any user after completing a successful match with the person.
To send a message to any registered user, click on ‘Contact’ after opening the person's profile.